Method and apparatus for the continuous treatment of granular and/or powdered material with steam and/or gas



3,3 F GRANULAR /OR GAS Jan. 23, 1968 w. FRIEDRICH METHOD AND APPARATUSFOR THE CONTINUOUS TREATMENT O AND/OR POWDERED MATERIAL WITH STEAM ANDFiled Jan. 26, 1965 United States Patent Ofitice 3,364,583 Patented Jan.23, 1968 3,364,583 METHOD AND APPARATUS FOR THE CONTINU- OUS TREATMENTOF GRANULAR AND/OR EOg/DERED MATERIAL WITH STEAM AND/ OR A WolfgangFriedrich, Braunschweig, Germany, assignor to Miag Muhienhan undIndustrie G.m.b.H., Brannschweig, Germany, a German company Filed Jan.26, 1965, Ser. No. 428,169 Claims priority, application Germany, Jan.31, 1964, M 59,757 2 Claims. (Cl. 34-10) The invention relates to amethod of continuously treating granular and/ or powdered material withsteam and/or gas which rises vertically with deceleration against adownward stream of continuously fed material at a speed exceeding thefloating speed, the material being fed at such a rate that clouds ofmaterial are formed which have an independent flow behaviour and whichon attaining sufficient density drop through the point of maximum gasvelocity, in succession, to be successively removed.

The gas for treating the material flows upwardly through the apparatusfor carrying out the method, which apparatus comprises a downwardlytapering vertical tank with a nozzle at the bottom and outlets for thegas and inlets for the material at the top, the gas then passing ino aseparator in which the gas is freed of entrained material, which is thenrecirculated to the vertical tank.

In some uses of the present method it is necessary to recirculate thematerial several times, that is, it is necessary to remove the materialfrom the tank with the tank, to separate it from the gas and then toreturn it to the tank in order to achieve the requisite duration ofpretreatment. This makes it necessary to use a very extensive separatingplant if large quantities of circulating material are to be treated inthe desired manner. When the separating system is large there is thefurther disadvantage that the gas passing therethr ough loses pressure.

According to the invention a method is proposed for overcoming thesedisadvantages which comprises causing the clouds of materialsuccessively dropping out of the vertical tank to pass into anotherrising flow of gas.

The invention further includes suitable apparatus for carrying out thismethod.

The material is fed into the upper vertical tank, where it is treated bythe gas until a cloud of material forms and drops through the nozzle ofthe upper tank to pass into the next or bottom vertical tank, where itis further intensively treated until it drops out of the second tank topass either into a third vertical tank or to a station for treatment ofa different nature.

The invention is further described with reference to embodimentsillustrated in the accompanying drawings, in which:

FIG. 1 is an elevation of an assembly of three vertical tanks insuperposition;

FIG. 2 is a fragmentary elevation of an assembly according to anotherembodiment of the invention, in which several upper vertical tanks,connected in parallel, are used in place of a single upper verticaltank; and

FIG. 3 is a perspective representation of a processing tank of polygonalcross-section.

Referring to FIG. 1, the apparatus for carrying out the method of theinvention comprises three superposed vertical tanks 1, 2 and 3. Each ofthese vertical tanks tapers downwardly to terminate in a nozzle 11, 21,and 31 respectively. The upper vertical tank 1 is closed by a cover 12in the form of a hollow frustum. A plurality of separators 4, connectedin parallel, are provided whose intake conduits 41 are connected to thecover 12. In the center of the cover 12 there is disposed an admissionpipe for the untreated material.

The second vertical tank 2 has a cover 22 which has a large centralopening over which the nozzle 11 of the tank 1 fits. The materialseparated in the separators 4 is collected in sluices 43 and passesthrough spouts 42 to be returned to the processing apparatus. It is inmost cases possible for the spouts 42 to pass through the cover 22 andthus guide the recirculated material into the second vertical tank 2, asthe thorough pretreatment which is provided in the upper vertical tank 1is usually sufiicient, particularly if the treatment provided in thesecond tank 2 is to be followed by further treatment in a third tank 3.This possibility is illustrated on the left hand side of FIG. 1. In somecases, however, it may be necessary for the material to be recirculatedinto the upper vertical tank 1, as illustrated on the right hand side ofFIG. 1.

The second vertical tank 2 rests on the cover, designated by 32, of thetank 3, the nozzle 21 fitting over a central opening in the cover 32.The pretreatment of the material is completed in the tank 3, from whichthe material passes, via the nozzle 31, to an apparatus 6 for treatmentof a diiferent nature.

FIG. 1 shows that the cross-section of the nozzles 11, 21 and 31decreases progressively from top to bottom of the assembly. Thisarrangement is suitable in the case where the temperature of the gas orsteam does not substantially change as it rises through the successivetanks 3, 2 and 1. In cases where the gas temperature does substantiallychange as the gas rises in the assembly the difference in cross-sectionof the nozzle will not be pronounced. In some cases the eifect of thetemperature change may even exceed that of the difierent nozzlecrosssections so that the cross-sectional area of the nozzles mayincrease from top to bottom whilst the velocity of the gas stilldecreases as it rises in the assembly. It is advantageous for thevelocity of the gas to decrease as the latter rises in the assembly,since this reduces the tendency of the gas to entrain a large proportionof the material during the upward movement of the gas. Thus theinfluence of the material entrained towards the top, where the untreatedmaterial is admitted, is reduced and it is possible to employ smallseparators.

In FIG. 1 a plurality of separators 4 are disposed around the uppervertical tank 1, but in the embodiment shown in FIG. 2 there is thereverse arrangement, that is, a plurality of vertical tanks 1' aredisposed around a single separator 4' which is arranged in the centreline of the second vertical tank 2' and which discharges therecirculated material into the tank 2'. The untreated material is fedthrough admission pipes 5" to the vertical tanks 1 whose covers 12 havecentrally connected suction conduits 41 which are connected to theseparator 4. The separator 4 is equipped in the manner described in themain patent. This arrangement normally makes it possible to decrease theoverall height of the assembly.

Further progress in this direction may be made by making the upper oruppermost vertical tank or tanks annular, the line 13 representing thegeneratrix of the inner Wall of said annular tank and the line 14representing the generatrix of the outer wall thereof. Thecross-sectional representation of the arrangement shown in FIG. 2 is notchanged by this alternative possibility. The above-described annulartank may have a plurality of contiguous and overlapping covers 12', eachcover being fitted with a gas discharge pipe 41'. In some cases the topvertical tank need not be in the form of a continuous ring but maycomprise a plurality of vertical tanks, for example two, which are inthe form of a circular ring sector and somewhat resemble a shell inappearance. The nozzle of such a tank has a polygonal, in fact arectangular cross-section of which two of the sides are curved, or inother 3 words, the cross-section has the form of a circular ring sector.

From this arrangement may be developed the conception of making thevertical tanks not round but polygonal, particularly quadrangular andpreferably rectangular, the defining cross-sectional lines beingstraight. This embodiment is shown in perspective in FIG. 3. It providesa simple means of repeatedly carrying out a once tried process for thetreatment of material under the same conditions and independently of thequantity of material passed through, per unit of time. It is simplynecessary to make the length 7 of the tank 8 shown in FIG. 3 such thatthe tank can cope with the desired rate of flow of the material. Thetank 8 has a cover 82 which may be connected to a quadrangular conduit 9or, in a manner similar to that illustrated in FIG. 1, may be connectedto a nozzle of a superposed vertical tank resembling the tank shown inFIG. 3 but differing therefrom mainly in the width 10 of the nozzles.

It is normally convenient for the gas discharge conduits 9 leading tothe separators to have a rectangular crosssection. If it isadvantageous, however, to use round pipes for this purposes, therectangular nozzle cross-section shown in FIG. 3 can merge into a roundtank whose cover is connected to a round pipe. This possibility is notshown.

This change in cross-section requires more complicated manufacturingtechnique, but the shape produced has no detrimental eflect on theprocess, as it is in fact desirable to avoid stationary flow conditionsin the vertical tanks in the interests of forming a cloud of material ina state of maximum turbulence.

Changes may be made within the scope and spirit of the appended claimswhich define what is believed to be new and desired to have protected byLetters Patent.

1 claim:

1. Apparatus for the continuous treatment of granular and/or powderedmaterial with a fluid such as steam and/or gas, comprising at least onevertical tank which tapers downwardly, terminating at the lower endthereof in a nozzle and having in the upper end thereof a fluiddischarge opening, means operatively connected with each such tank forsupplying thereto material to be treated, at least one further verticaltank terminating at the lower end thereof in a noule, and having in theupper end thereof a fluid discharge opening, each further tank beingarranged in superposition below said first tank with its fluid dischargeopening in serial communication with the nozzle of the preceding tank,the nozzle of the lowermost tank forming the inlet for the treatingfluid, the respective nozzle cross-sections being so successivelydimensioned from top to bottom that the rising fluid is alternatelyaccelerated and decelerated, with the velocity of the rising fluidimmediately following each acceleration becoming progressively less asthe fluid rises, and a plurality of separators disposed laterally aroundsaid top tank for withdrawing material from the fluid discharged throughthe fluid discharge opening of the top tank and arranged to dischargewithdrawn material into a tank disposed below said top tank 2. A methodfor continuous treatment of granular and finely divided particles ofmaterial in a counter-flowing highly compressible fluid flowingupwardly, in which such material is treated Without essential change asto form and weight of the particles, comprising the steps of effectingcontinuous flow of the fluid in an upward direction with such fluidrising with decreasing velocity, alternately decelerating andaccelerating such fluid as it rises, introducing said material into saidfluid flow in a direction counter to said fluid flow, continuouslymaintaining the velocity of said fluid at a rate higher than thatrequired to maintain suspension of the material particles, controllingthe amount of material added per unit of time to the fluid to effect acompression of such material and thereby form successive clouds whichreach a density suflicient to fall through an intermediate area of fluidacceleration to a much larger area adjacent thereto, thus falling intoanother decelerating flow of fluid, passing the respective clouds ofmaterial through at least one additional intermediate area of fluidacceleration to a much larger area adjacent thereto, thus falling intoat least one additional deceleration flow of fluid, with the maximumvelocity becoming progressively less as the fluid stream rises, andthereafter removing the material from said fluid.

References Cited UNITED STATES PATENTS 2,659,587 11/1953 Bowen 34-572,663,560 12/1953 Muller et a1 2615-32 X 2,866,625 12/1958 Sylvest 34-573,067,990 12/1962 Zacpal 26332 3,083,472 4/ 1963 Helming 3457 3,135,5886/1964 Helming 34-57 3,140,862 7/1964 Schoppe 3410 X 3,207,494 9/1965Jager 26 3--32 3,265,775 8/1966 Friedrich 26 3-32 FREDERICK L.MA'ITESON, 1a., Primary Examiner.

J. J. CAMBY, Assistant Examiner.

2. A METHOD FOR CONTINUOUS TREATMENT OF GRANULAR AND FINELY DIVIDEDPARTICLES OF MATERIAL IN A COUNTER-FLOWING HIGHLY COMPRESSIBLE FLUIDFLOWING UPWARDLY, IN WHICH SUCH MATERIAL IS TREATED WITHOUT ESSENTIALCHANGE AS TO FORM AND WEIGHT OF THE PARTICLES, COMPRISING THE STEPS OFEFFECTING CONTINUOUS FLOW OF THE FLUID IN AN UPWARD DIRECTION WITH SUCHFLUID RISING WITH DECREASING VELOCITY, ALTERNATELY DECELERATING ANDACCELERATING SUCH FLUID AS IT RISES, INTRODUCING SAID MATERIAL INTO SAIDFLUID FLOW IN A DIRECTION COUNTER TO SAID FLUID FLOW, CONTINUOUSLYMAINTAINING THE VELOCITY OF SAID FLUID AT A RATE HIGHER THAN THATREQUIRED TO MAINTAIN SUSPENSION OF THE MATERIAL PARTICLES, CONTROLLINGTHE AMOUNT OF MATERIAL ADDED PER UNIT OF TIME TO THE FLUID TO EFFECT ACOMPRESSION OF SUCH MATERIAL AND THEREBY FORM SUCCESSIVE CLOUDS WHICHREACH A DENSITY SUFFICIENT TO FALL THROUGH AN INTERMEDIATE AREA OF FLUIDACCELERATION TO A MUCH LARGER AREA ADJACENT THERETO, THUS FALLING INTOANOTHER DECELERATING FLOW OF FLUID, PASSING THE RESPECTIVE CLOUDS OFMATERIAL THROUGH AT LEAST ONE